Protective composition and use thereof



Patented Oct. 1, 1940 I UNITED. -Es

I 2,216,362 v rao'rizonvacomosnIoN AND USE I manor j William Courtney Wilson and Paul H. Yoder, ciiicago, Ill., assignors to Pyro xylin Products; Inc.',

Chicago,.lll., a corporation of Illinois No Drawing.

The present invention relates toa new'composition of matter having ordinary, special and new uses and advantages. It relates to the'arts of protecting surfaces, of water proofing, of mois-Q ture-vapor-proofing, and of packaging, byusir'ig,

the composition as a coating; film, wrapper,- orf the like. Ithas special use onpackagedgoods; as a coating on a package, or as a wrapper, or a coating on a wrapper. In such use it avoids blocking" or sticking of packages togethenespe-J cially, when hot, as in packaging; shipping or storing. r H 7 Many articles such as foodstufi's, tobacco, etc; are now packed in metallic containers in order to preserve them in a fresh condition over a period of time. Fiber containers are alsoused for this 3 purpose, but where moisture is a factor it has] heretofore been common practice to coat or impregnate the container, or the paper wrapp f with a wax, as for example with paraflin wax. Waxes, however, soften at relatively .warm summer temperatures and in heated storerooms, and. the surfaces frequently stick to each other, and may be damaged in separating them. Waxed articles in cold environments become brittle and break at the folds thus admitting moisture. In either case there may be formed an unsightly package. More recently, the use of nitrocellulose lacquers containing a wax, as for example products such as those described in U. S. Patent No. 1,826,696 to Charch andPrindle have found" extensive use for coating a regenerated cellulose sheet to render it moisture-'vapor-proof.

While the use of nitrocelluloselacquers "con-1,.

taining a wax produces a coating having r'elatively good moisture-vapor-proofing qualitiesQther are certain difiiculties in the use of such protect-t, ing coatings, and especially where such coatings are used on paper or paper productsisuch as car- 40ton stock, as compared to dense smooth materials such as a sheet of regenerated. cellulose. For example, there is substantially no penetration. of organic solvents into regenerated cellulos'e,-f whereas there is not only penetration;v but per-. sistent retention of many solvents into fibrousfl cellulosic'materials such as paper. Because of the nature of the solvents required to hold the cellulose nitrate in solution, it is'often 'diflicult. to remove many of the solvents to such an extent as to leave no odoran important factor in food packaging. Furthermore, solvents such as esters I and alcohols are apt to affect colors or inks,' where the coating is applied over'printed or secorated surfaces, and cause many of the coloring 55. materials of the inks, such as toners, dyes, etctc' Application February 4, Serial No. 124,03

12 chips. rotor-Lon fpensive'solvents required; but also because a re1- vatively-heavy coating is required, as compared'to U that requiredonadense smooth material such I the use of nitrocellulose-wax compositions; is the tons are packed, and in other'ways, thus produc'-- which may be selected so as not to leave odors,

films; One of the prime objects of our invention isto produce a moisture vapor-prooi' composition th'atiretains its moisture-vapor-proofing charac bleed, and. change lose-wax coating; so that difflculty is encounteredv in applying stickers, or in gluing the laps? of coated -labels,- or the folds of a carton that is so coated. ThGxCOSt'. of moisture-proofing paper,

carton stock, etc. with a nitrocellulose wax coating is relatively high, not only because of the ex- .1

as regenerated cellulose, or cellulose acetate films. l A very important and serious disadvantage of tendency of the wax tofsweat ou at somewhat elevated temperatures. .Waxes in general are not ."compatible to any" great extent with nitrocellulose, and it 'is almost esse'ntial that such coating compositions be dried above the melting point of the wax. Even when so prepared, such coatings, when'reheatedl sweat out considerable quanti-- ties of the wax, and thewax which appears on the-"surface is easily removed by wiping, and is readily so removed in handling. An example of this ,difliculty is encountered in the packaging of salt, cheese, soap, etc. which are packed hot.- When the' hot material, such as table salt (packaged at from to F. to secure free screena ing) is placed in acarton coated with-a nitrocel in the coating comes to the, surface, and is' re- I moved in many areas .by mechanical or manualv handling, or'by coming in contact with other cartons, or with the fiber box in which the car ing areas of row orvoid moisture-proofingquality, impairing the value of the coating, and defeating'its purpose. v

' an object of our invention is to produce aprotective coating which'i's also a moisture-vaporproofing composition, and which employs relatively inexpensive -and'unobjectionable solvents or seriously; to affect printing inks. Another object-is to produce a moisture-vapor- -proof composition' that has jafhigh resistance to moisture-vapor-penetration, even when employed in thin teristics at'relatiyely high temperatures-and upon I the color and appearance of the printed design; Also. it-is difflcult to secure an adhesive union to such 'aproofing nitrocellu- 'may also employ modifying agents, such as plasticizers to secure greater flexibility, coloring agents, mere diluents, resins, waxes, etc. These materials may be mixed in various proportions,

depending on the qualities desired, but we prefer to use the rubber derivative in an amount substantially greater than the amount of metal soap.

As rubber derivatives we prefer to use a condensation rubber derivative having the characthe use of a condensation derivative of rubber.

The latter is characterized particularly by softening with heat to a.degree that it becomes tacky at a giventemperature, herein referred to as the tacky point. When heated to the tacky point, protective coatings consisting of this material alone frequently stick, or a mass of packages protected with it will block. Where a moistureproofing wax is added to it, the resulting composition will block at even lower temperatures than the same composition without the wax. While higher-melting modifications of these rubber derivatives may be made, we have found that an increase in the softening or tacky point is accompanied by an increase in brittleness. When plasticizer is used to overcome this increased brittleness the softening or tacky point is correspondingly lowered, so that little or no improvement, as regards blocking, is secured.

By means of the present invention a new and different agent is employed, namely the metal soap, which not only avoids the bad effect of wax in making the product tacky at a lower temperature, but which renders it less tacky than the rubber derivative alone at any given temperature. In other words, the temperature at which tackiness or blockingmay occur is raised, rather than lowered, by using the metal soap in place of a wax. Thus the present invention affords a product which may be used in cases where the prior art product cannot be used.

Some of the rubber derivatives suitable for use in our invention are described in an article entitled Plioform-A New Molding Resin, Journal of Industrial and Engineering Chemistry, vol. 26, page 123, February 1934, by H. R. Tides and A. M. Clifford of The Goodyear Tire & Rubber Company, Akron, Ohio. One product is also known os Pliolite" and is referred to as Pliolite in an article by said H. R. Thies, on page 22 of Paint, Oil and Chemical Review, issue of April 18, 1935. Especially useful are the products obtained by the reaction of rubber with stannic chloride, ferric chloride, boron fluoride, chlorostannic acid, etc.

The formation of such products is described in prior U. S. Patent No. 1,751,817, No. 1,797,188 and No. 1,846,247, wherein numerous halides of metals and chlorostannic acid are disclosed as reagents and are characterized generally as constituting a group consisting of chlorostannic acid and halides of amphoteric metals. Among such products may be mentioned the product sold under the trade name of Pliolite, manufactured by the Goodyear Tire and Rubber Company of Akron, Ohio, which is described in a public bulletin by the manufacturer as an amber colored thermoplastic solid, having a softening point of 55? to 65 C. and a specific gravity of 1.047. It contains more than 92% by weight of rubber hydrocarbon. Oneway in which such a product may be secured is to dissolve, for example, 10 parts of milled rubber with a plasticity of about 300, in 90 parts of benzol to which is added 1 part of chlorostannic acid. The mixture is refluxed until the desired condensation has taken place. The solution is filtered, and poured into water, or preferably water in which a reducing agent such as sodium sulfite has been dissolved to minimize oxidation. The benzol may be removed by steam distillation, and a fine powder of the rubber condensation product is precipitated.

The powder obtained as above is suited for our use. The metal soap may be dispersed into the powder or other form of the material of such powder, for example by milling, as on rubber-' rolling mills or by mechanical working, as in a Banbury mixer, or with a heavy dough mixer. A small amount of solvent may be advantageous, as when a dough mixer is used. The precipitated rubber derivative described above may be milled prior to dispersing the soap therein, and the metal soap may be added as a solution or dispersion in a solvent, as for example toluene or a suitable petroleum fraction.

Other condensation products of rubber are known, such as those made by use of paratoluene sulphonic acid. This type for example is not soluble in the gasoline-type of solvents. Those prepared in solution are preferred, such as first above described, since they may be made colorless and transparent, and are more universally soluble in organic solvents.

As water-insoluble metal soaps, we have found that a wide variety may be employed and the selection depends in part upon the nature of the However, such coatings may be applied to give smooth films by coating machines that shear the wet liquid or plastic film, as for example the machine described by Fawkes and McKenzie in U. S.

of natural and artificial waxes, as for example parafiin wax, montan wax, ceresin, spermaceti wax, beeswax, halowax, etc., the waxes do not sweat out when the composition is exposed to relatively high temperatures. We may, therefore, use waxes in combination with the metal waxes is effective in rubber derivatives as well as in nitrocellulose base compositions, but the wax is retained in the rubber-derivative compositions under conditions where it sweats out in nitrocellulose compositions. We do not claim moisture-vapor-proofing waxes alone as our invention, but do claim them in combination with metal soap. We know that in general waxes alone used as moisture-vapor-proofing agents will cause the composition to become more sticky or tacky at less elevated temperatures than the same composition without the wax. We have found that a combination of wax and metal soap may be used which does not so early become tacky or sticky with increasing. heat, which does not becomesubject to injury while hot, by scufiing or rubbing, and which is capable of being heated and cooled without loss of moisture-vapor-transmission resistance. combination, the metal soap and the wax contribute such moisture and other resistant properties, but the metal soap is the essential agent of our invention for that purpose. may be an auxiliary agent for contributing such resistance, but it also maybe a plasticizer. In our invention the wax may be one which is a plasticizer, or one whichhas some other function, or one which is poor or lacking in the property of imparting moisture-vapor-resistance in a combination with a rubber derivative. Therefore, our invention contemplatesuse of a wider range of waxes than used heretofore in moisture-proofing compositions. X

As solvents we prefer to use hydrocarbons because of their low cost, because of the ease with which hydrocarbons may be eliminated by evaporation, and because of their freedom from residual odors.- Furthermore, hydrocarbons have less tendency to soften the ink, or to bleed. the pigments of the inks, than do more powerful solvents such as alcohols, esters, ketpnes, etc.,

such as are used in nitrocellulose lacquers. For

the preferred condensation derivative of rubber we may use either aliphatic (petroleum) hydrocarbons such as varnish makers and painters naphtha, or their derivatives such as chloroform, or aromatic (coal tar) hydrocarbons such as toluene, or' their derivatives such as chlorbenzol. We do not, however, preclude the use of other I solvents when such solvents are useful or desirable but in general we prefer to usehydro carbons, because of their low cost and the ease with which they may be eliminated. Simple or mixed solvents may be used.

The metal soap may be incorporated with the rubber derivative in a variety of ways. .One

method. is to dissolve or disperse the soap in a portion of a solvent, using heat if necessary, and addthe soap solution to a solution of the rubher-derivative. Another method is to grind or masticate the metal soap with the rubber derivative, as for example on roller mills, or in a heavy duty dough type mixer, or in a Banbury mixer, using some solvent if necessary. In'general we have found it preferable to masticate the rubber derivative and metal soap to secure a high dispersion 'of the soap, and a better gloss.

A resin orresins may be added to secure'be'tter adherence where the composition is to be applied so asto be carried by a surface. Resin also j may ,increase the gloss. .It may be added as a In" such The wax V aflin or other wax.

' purposes. The resin used should be compatible with the rubber derivative, and should of course be soluble in the solvent employed. Examples of suitable resins are the cumar and indene resins, hydrogenated rosin-glycerol esters, etc. These resins may be added in any convenient manner as for example as solutions, or they may be milled into the rubberderivative, as for example on a Banbury mixer, or on differential rolls. This may be done when the soap is added or at another time. l I

In order to illustrate our invention the following examples are given merely as illustrations of several phases of our invention. It is, of course, to be understood that these are illustrative formulas only,,and that wide departures from these examples may be made within the scope of our invention as will be understood by those skilled in the art.

- Example I I Parts by weight Condensation derivative of rubber, such as v Pliolite" 135 Magnesium stearate l5 Toluol, or'other solvent 850 I The magnesium stearate may be incorporated in any convenient manner.- For example the magnesium stearate maybe dissolved in the toluol before the rubber derivative is added; or a heavy solution of the rubber derivative may be dissolved in a part of the solvent to produce a very viscous solution, and the magnesium stea-,

rate dispersed in the heavy solution in a dough mixer, or by grinding on three-roller mills; or

the magnesium' stearate may be-milled into the rubber resin (before it is dissolved). on a rubber-rolling mill of the type used for making rubber compositions, or in a Banbury mixer. In general the product produces a glossier finish as the'solvent is decreased in combining the rubber derivative and the metal soap. The composition of Example 1 is suitable for coating paper and other materials to produce waterproof coatings that have ahigh degree of moisturevapor-proofness. Furthermore, since the tacky point of therubber derivative is lower than that of the composition there is less tendency for the composition to block" when used as a coating than is the case where the same rubber derivative is used by itself, or with a wax.

Example 2 Zinc palmitate is substituted forthe magnesium stearate of Example 1.

Example. 3; I Parts by weight Condensation derivative. of rubber, such as Pliolite 225. Paraflln 12.5 Zinc palmitate 12.5- Toluol or other solvent 585.

This composition results in a coating somecause of the plasticizing functionof paraffin, and isespecially useful for coating thin caliper paper and other materials that require a considerable degree of pliability. The paraff n does not sweat out on heating.

sticky to 'heat block than do coatings consist ing only of the same rubber derivative and par- Such a coating has 'much'less tendency to soften and l to become sufficiently what more flexible than Examples l and 2 be- 765 Example 4 Parts by weight Condensation derivative of rubber, such as- Pliolite 81 Cumar resin 9 Zinc palmitate 6 Paraffin wax 4 Toluol or other solvent 234 Example Zinc laurate is substituted as the metal soap in Examples 1, 3 and 4.

The composition of- Example 4 has a heatblock temperature of about 170 F. under certain test conditions. By the same test, a composition like the above wherein the metal soap is changed to the same amount of parafiin wax (in addition to that already present), the heatblock temperature is about 115 F. Compositions generally like those of Examples 1 to 5 may readily be made with a heat-block temperature to withstand live steam by selecting specific materials and proportions.

To show that the combination using the condensation derivative of rubber is of a difierent character than a similar combination using a rubber hydrochloride, or a chlorinated rubber, the following examples are given, serving as a basis for the comparisons in the table below.

Rubber condensation derivatives are extremely stable and are substantially neutral. In general, {or paper coating work, we have found that rubber derivatives containing relatively large amounts i of halogens tend to lower the strength of the paper and cause it to become more brittle and fragile, especially upon aging.

In order to determine the relative merits of coatings intended for moisture-vapor-proofing, we have used a modification of the method described by Abrams and Chilson in the Paper Mill page 24, September 20,1930, and also Abrams and Brabender Paper Trade Journal, April 9, 1936, page 32. In this method a coating of known weight per 1000 sq. ft. is placed on a backing to be moisture-vapor-proofed, such for example as paper, (Glassine, printed stock, carton stock, etc.) or cloth, or any other sheet-like material that can be placed over the cup. If only one side is coated, the coated side should preferably be placed next to the zone of high humidity. In the tests described below, the coated side was thus placed outward. Calcium chloride was placed in the cup, and the cup placed in a cabinet maintained at 90 F., and having air therein at a relative humidity of 98%. The air within the cabinet was kept in motion by means of rotating paddles. By weighing the test cups at regular intervals, and determining the increase in weight, due to moisture absorption of the calcium chloride through the coating, the moisture transfer per 100 sq. in. per 24 hours is calculated.

Tests carried out in the above manner gave the following results on'samples of the various coatings applied to one side of Glassine paperdescribed herein:

Table Grams per 100 sq. in. per 24 hrs.-

It is to be understood that other metal soaps which are water-insoluble may be used besides those illustrated in the foregoing examples. Among these may be mentioned the stearate, palmitate, oleate, laurate, etc., of calcium, magnesium, lead, zinc and other metals yielding waterin'soluble metal soaps which are well known to the art. We may employ single or mixed simple or complex metal soaps of this character. By a complex metal soap we refer to one in which more than one soap-forming acid is combined with one metal.

It is also to be understood that other solvents may be used, or mixtures of'solvents such as various petroleum solvents, and coal tar hydrocarbons such as benzol, xylol, etc., as well as chlorinated solvents such as carbon tetrachloride,

chloroform, ethylene dichloride, etc. The choice of the proper solvents may be readily exercised by anyone skilled in the art, and may be varied to secure different drying rates, to secure increased solvent power, to vary the viscosity at a given concentration, etc., v

Furthermore, we may introduce other plasticizing agents such as various oils, either vegetable or mineral oils, as for example tung oil,

linseed oil, either treated. or raw, etc.

We may also introduce various coloring agents, such as dyes, pigments, etc., in order to produce colored coatings either transparent or opaque, it being understood that the examples given above produce substantially colorless transparent coatings. Various resins, either natural or synthetic, which are compatible with the rubber derivatives may also be used. Furthermore, we may use mixtures of various rubber derivatives where they are compatible, as for example we may use both chlorinated rubber and a condensation derivative of rubber in the same composition, all without departing from our invention.

Our compositions are especially useful for rendering printed cartons waterproof and also moisture-vapor-proof, and may be present on the cartons initially where such cartons are to be used for packing hot materials, such as salt, cheese; soap, etc., or where the composition is liable to be exposed to a wide range of temperatures. .Our coatings may be made so as not to soften and block at the temperatures used for packing these materials. Furthermore the moistureproofing agent does not sweat out and move to the surface. Thepackages may be handled hot without danger of rubbing off anything which has been exuded from the composition by heating, and they may be handled without scarring the surface. A particular advantage of the product of this invention is the property of resisting transmission of sodium chloride.

thin -or thick liquids, oras pastes .to form a continuous film. The solvent is removed from such films by evaporation with or without heating, and a the residue leaves a coherent continuous film having the desired properties. On. most-mate'- rials it will form an adherentcoat with varying force of adhesion, depending upon the composition and the form or material of the surface coated. Some surfacesmay be-cliosen' to permit stripping to leave a tenuousfilm of the composition itself. For example, certain amalgams', -'or mercury, or low-temperature fusible metalsmays be coated to make such' films. -maybe formed almost completely dry of the solvent, as in a rubber calender-machine.) Such 'coatings may then be permitted to lose solvent to set the solute in coherence, thus to complete the film in' situ for example on asheet of cloth passing through calender rolls.-

All kinds of materials maybe thus protected in several ways, such'as regenerated cellulose, cellulose acetate or other cellulose derivative films or forms, paper, woven fabric, vinyl compounds, sheets or other forms of casein, gelatin, prolamine, such as zein, wood, metal, etc.

Any container coated inside or out or impregnated and coated with the composition of this invention is considered as a new and improved. container with properties distinctive over like containers heretofore made, For example in the salt-packaging industry where salt is packed at 150 to 170 F. in machines wherein the containers are in close contact with each. other orwith mechanical parts, or human hands, the composition is heat-resistantynot subject to injury by ordinary contact or wiping, moisture-vaporproof and non-tacky when hot, and it' remains moisture-vapor-proo'f' when cold.- Upon these characteristics depends the success ofithe hotpacking operations to provide. a'-permanently .moisture-vapor-proof container in v the retail trade. At the present time containers with fiberor metal ends and paper'carton-stock walls, are

replacing all-metal containers. This replacement can be extended readily where the fiber sides can be made water-proof, moisture-vapor proof, and heat-resistant for certain uses. The present in-' vention therefore provides a fiber container, for example, for the hotpackingof salt, which is new, because it is capable of-successful usewhere others fail.

In commerce temperatures as high as 120 to 125 F. are commonly encountered, as in box-cars,

holds of ships, warehouses, etc. Underthis in- V dissolution or dispersion in a volatile vehicle to form a simple coating composition. To constitute a composition of matter under this invention, the ingredients need not initially be in the required or preferred proportion to form the type of coating above described. It is possible for example to-incorporate an excessive amount'of the soap into a rubber derivative, as -by mastication, to form a compound orfmaster batch which may be used thereafter with more of the same'or different rubber derivative, by dissolving, milling or other suitable method. w I

In the claims the term mini" is intended to "comprehend an independent unattached film as fact that'the addition of the snap renders a condensation derivative of rubber non-tacky at a temperature when it would otherwise be tacky and induce blocking, is a suflicient advantage to claim'such a simple mixture as a new and useful composition of matter. For this reason the met- 'al soap need not always be selected for its high moisture-proofing qualities. We claim:

1. A chemically stable solid composition of matter comprising in homogeneous admixture a major portion of the reaction product of rubher with a reagent from the group consisting of chlorostannic acid andhalide of amphoteric metal, and a minor quantity of water-insoluble metal soap of a fatty acid, said soap imparting increased resistance to water-vapor transmission and elevating the temperature at which the composition becomes tacky compared to the same composition without said soap.-

2. An article having a moisture-vapor-transmission resistant coat, said coat being the composition of claim 1.

3. A moisturevapor transmission resistant film consisting of the composition of claim-1.

4. A flowable composition comprising the composition of claim 1 and solvent therefor.

I 5. A liquid dispersion comprising the composition of claim 1 and a volatile liquid dispersing agent therefor.

tion product of rubber with a reagent from the group consisting of chlorostannic acid and halide of amphoteric metal, and water insoluble metal soap of fatty acid, the compound being capable of dilution with an additional amount of saidreaction product to impart to said additional amount increased moisture-vapor transmission resistance andan elevated tack-providing temperature.

-'7. The method of raising the heat-block temperature of a composition consisting in major portion and essentially of the reaction product of rubber with a reagent from the group consisting of chlorostannic acid and halide of amphoteric metal, which comprises dispersing water-insoluble metal soap of fatty acid in said reaction product in quantity less than said reaction product. 7

8. The method of providing a moisture-vaportransmission-resistant barrier, which comprises forming a continuous chemically stable film comprisingin major proportion and essentially the reaction product of rubber with a reagent from the group consisting of chlorostannic 'acid. and halide of amphoteric metal, and dispersed therein a minor quantity of water-insoluble metal soap of fatty acid.

' 9. The method of providing a moisture-vaportransmission-resistant barrier, which comprises applying to a surface a liquid dispersion containing solid ingredients in a volatile liquid,

evaporating the volatile liquid to provide a continuous chemically stable film containing said solid ingredients, said film containing a major portion of the reaction product of rubber with a reagent from the group consisting of chlorostannic acid and halide of amphoteric metal,

' into rubber compounds, consisting of the reacble of drying to form a coat which is non-tacky at normal atmospheric temperatures.

10. The method of raising the heat-block temperature of a composition consisting in major portion and essentially of wax and the reaction product oi rubber with a reagent from the group consisting of chlorostannic acid and halide of amphoteric metal, which comprises dispersing water-insoluble metal soap of fatty acid in said reaction product in quantity less than the quantity of said reaction product.

11. A chemically stable solid composition of matter comprising in homogeneous admixture a major portion of the reaction product of rubher with a reagent from the group consisting of chlorostannic acid and halide of amphoteric metal, wax, and a water-insoluble metal soap of afatty acid in quantity less than the quantity of said-reaction product, said soap imparting increased resistance towater-vapor transmission and elevating the temperature at which the composition becomes tacky compared to the same composition without said soap.

12. The method of providing a moisturevapor-transmission-resistant barrier, which com prises forming a continuous chemically stable film comprising in major proportion and essentially the reaction product of rubber with 'a reagent from the group consisting of chlorostannic acid and halidegof amphoteric metal; wax, and dispersed therein a quantity of water-insoluble metal soap of fatty acid, which is less than the quantity of said reaction product.

WILLIAM COURTNEY WILSON. PAUL H. YODER.

CERTIFICATE or GORRECTION. Patent No. 2,216,562. October 1, 19!;0.

WILLIAM COURTNEY WILSON, ET AL- 3 It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as followss Page'Z, first column, line 61, for "0s" read --as--; page5,first column, line 55, be-

fore the words "we do not" insert the following sentence --'I'he solvent selected must be capable of producing a satisfactory dispersion or solution of the ingredients.--;

d, th t the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 29th day of October, A. D. 19 40.

Henry Van- Arsdale, (Seal) Acting Commissioner of Patents. 

